Recently, we have demonstrated than an epoxide metabolite of arachidonic acid (AA) (i.e. 5,6-epoxyeicosatrienoic, 5,6-EET) is a potent eicosanoid prolactin (PRL)-releasing agent in anterior pituitary (AP) cells, in vitro. These studies represent the first such unambiguous demonstration for epoxide metabolites of AA in PRL secretion and have important implications for basic mechanisms in hormone stimulus-secretion. We plan to extend the studies of EET action to include pharmacological modulation and mechanism studies to examine a role of cytochrome P-450 and other enzymes of AP cells in the metabolism of AA to active PRL-secreting agents. The studies will be divided into two major sections; (1) Studies of hormone modulation and mechanism of EET PRL-releasing action, and (2) Studies of the metabolism and mechanism of anterior pituitary. We will test the novel hypothesis that 5,6-EET acts as a messenger to stimulate the secretion of PRL from AP cells. AP cells obtained from various animal pretreatments will be challenged with PRL-releasing agents and EET levels will be determined in parallel with PRL levels. The studies of EET mechanism of action will involve clonal anterior pituitary (GH3) cells and AP cells. Studies with GH3 cells will be carried out to determine if Ca2+ flux contributes to 5,6-EET mediated PRL secretion. The role of cytochrome p-450 in AA-mediated PRL secretion will be examined. First, the presence of P450 in AP cells will be determined. Regio- and stereoselective hydroxylation of testosterone will be employed to identify AP cytochrome P-450 isozymes. Using specific HPLC and RIA assays we will determine if EET metabolites of AA are increased in response to agents which elevate PRL secretion. A thorough understanding of EET action and biosynthesis may provide much information regarding the role of EETs in human physiology and disease states.